1. Field of the Invention
The present invention relates to current sensors, and particularly relates to a current sensor that measures a value of a current by detecting a magnetic field arising as a result of the current.
2. Description of the Related Art
Japanese Unexamined Patent Application Publication No. 2010-2277 and International Publication No. WO 2011/155261 disclose current sensor configurations.
The current sensor disclosed in Japanese Unexamined Patent Application Publication No. 2010-2277 provides a busbar, an insulating substrate, a Hall IC serving as a magnetism detecting element, and a magnetic shielding body for each of a U phase, a V phase, and a W phase. Each magnetic shielding body includes an upper magnetic shielding member and a lower magnetic shielding member, and thus constitutes an annular enclosure part that encloses the corresponding busbar, insulating substrate, and Hall IC in an annular shape. The magnetic shielding body thus blocks magnetism from external magnetic fields. A gap is formed between the upper magnetic shielding member and the lower magnetic shielding member. The position of the gap in a height direction is the same as or similar to the position of the busbar in the height direction, such that the gap is located in an area facing a side surface of the busbar. The Hall IC is disposed above a central area of the busbar.
The current sensor disclosed in International Publication No. WO 2011/155261 is a magnetic balance type current sensor, and includes: a magnetoresistance element whose characteristics change in response to an induced magnetic field from a current to be measured; a feedback coil that is disposed in the vicinity of the magnetoresistance element and generates a canceling magnetic field canceling out the induced magnetic field; a magnetic shield that attenuates the induced magnetic field and enhances the canceling magnetic field; and a hard bias layer, provided on or above the magnetic shield, that suppresses hysteresis in the magnetic shield.
Conventional current sensors are used in linear regions where the density of a magnetic flux detected by a magnetic sensor having a Hall element, a magnetoresistance element, or the like is proportional to an output voltage. In other words, when a conventional current sensor measures a high current that produces a magnetic field exceeding the linear region of the magnetic sensor, measurement error will rise and measurement accuracy will drop.
On the other hand, a current sensor including a magnetic sensor having a wide linear region may be used to measure a high current. However, the magnetic sensor has a low sensitivity in this case, which reduces the measurement accuracy for low currents.